Electrical circuits are often connected using electrical cables, such as wire, twisted wire pairs, wire ribbons, and coaxial cables. Shielded cables are used in some applications to avoid receiving electromagnetic interference, or to avoid transmitting electromagnetic interference along the cable. Some cable structures, such as coaxial cable used to couple relatively high-frequency electrical signal between electronic circuits, provide a shielding structure (e.g. the outer conductor) surrounding a signal-carrying structure (e.g. center conductor). Coaxial connectors support transverse electromagnetic wave (“TEM”) transmission over a broad bandwidth (frequency range), including direct-current (“DC”) transmission.
Coaxial connectors are used with coaxial cable to retain the advantages of the coaxial geometry, such as full shielding. Coaxial connectors are sometimes used to connect a coaxial cable to a planar transmission structure in a printed circuit board (“PCB”). Multiple metal layers in the PWB can provide essentially full shielding for signals traveling along transmission structures. Similarly, the coaxial cables are typically cut to the desired length and connectors attached, typically by soldering and/or crimping, to each end of the cable. Unfortunately, coaxial connectors are typically bulky and heavy. The ergonomics of such connectors (e.g. the ability to attach and remove the connector(s) by hand) limit the size of the connector and thus the interconnection density.
Flexible film cables (“flex cables”) are also used as cabling between electronic circuits. Flex cables are fabricated using photolithographic transfer processes similar to those used to manufacture PCBs. These processes allow several parallel transmission structures to be made in a single flex cable. Flex cables approximate the shielding of coaxial cable using multiple metal layers and interconnecting vias that are normal to the metal layers.
A variety of techniques have been used to attach flex cables to PCBs. One approach uses metal balls, such as solder balls, pressed against corresponding contacts on the PCB. Another approach uses array contacts, or multi-pin connectors. Unfortunately, these types of connections do not offer the benefits of a fully shielded flex cable connector interface.